The desire to reduce the cost and increase the ease and speed of refuse collection, in conjunction with improvements in automation techniques, has resulted in substantial changes in the collection of residential and commercial refuse. As the technology of carts and lift mechanisms developed, several different styles of carts and lift mechanisms have emerged. However, despite these differences, most modern refuse collection systems include carts having wheels, which allow them to be rolled to the street curb, where they are lifted and dumped by a semi or fully automated lift mechanism.
Regardless of the type of lift mechanism being used, there are common problems which each has attempted to solve. For instance, the overall size of the lift mechanism is an important factor. The width or profile of the lift mechanism has a dramatic effect on both the desirability of the device to potential purchasers and on the ease of use. Specifically, the width or profile of the lift mechanism may limit its use in cities which have narrow residential streets. In Europe for example, it is important to minimize the profile of the lift mechanism be as slender as possible so that the refuse vehicle can operate on narrow streets and in confined spaces. This desire to obtain a lift mechanism with a slender width or profile has resulted in several different approaches to the problem. For example, U.S. Pat. No. 4,057,156 to Thompson et al. discloses the use of track system which is attached to the side of the refuse vehicle for lifting and dumping the cart. A track mounted to the refuse truck has also been used by Applicant in its Foothill device. Similarly, U.S. Pat. No. 4,597,710 to Kovats uses a pair of vertical guide rails secured to a refuse vehicle for lifting and dumping a refuse cart.
An alternative approach is disclosed by Bayne et al. in U.S. Pat. Nos. 5,333,984, 5,308,211, and 4,773,812. Each of the Bayne et al. patents, utilize a reciprocating cylinder to activate a rack and pinion arrangement for rotating an output shaft attached thereto. The output shaft has a pair of arms attached at opposed ends thereof for rotation therewith. Bayne et al. state that the use of a rack and pinion arrangement to drive the output shaft solves the problem of a continuously smooth rotation of the lift mechanism throughout the operating cycle. In addition, Bayne et al. position two cylinders on the same side of the housing relative to the output shaft so as to narrow the profile of the lift mechanism and thereby attempt to solve the width problem. Others have also attempted to address the width and smoothness problems by utilizing similar arrangements; see for instance, U.S. Pat. No. 3,804,277 to Brown et al., U.S. Pat. No. 3,894,642 to Shive, U.S. Pat. No. 4,365,922 to Borders, U.S. Pat. No. 4,687,405 to Olney, and Applicant's Roto-Drive lift mechanism.
However, by attempting to address the problems of a slender profile and a smooth operation of the lift mechanism, the above-referenced approaches have created an additional problem. Specifically, the ability of the lift mechanism to smoothly handle a weight, often in excess of two (200) hundred pounds, without jerking is important from both a speed of collection and a maintenance cost perspective. In addition, the ability to effectively handle the weight of a cart which is slightly off center on the lift mechanism without causing damage to the lift mechanism due to the additional torsional stress is important to the mechanical longevity of the device. Although various prior art patents, such as the Bayne et al. patents, use a rack and pinion arrangement to drive the output shaft and thereby obtain a slender profile, such an arrangement has a negative effect on the overall lifting strength of the lift mechanism.
Furthermore, the use of the above-referenced approaches have a secondary problem in that they are often not well suited for dual use with both residential and commercial carts because of the additional size and weight normally associated with the commercial carts. Accordingly, a choice must be made to either limit the lift mechanism to residential carts or sacrifice the slender profile of their lift mechanism to accommodate larger components necessary to support the extra weight of commercial carts.
It is also uniformly desirable for the lift mechanism to be able to carry the refuse cart as far back into the hopper of the refuse vehicle as possible so that the operator of the refuse vehicle does not have to activate the compactor as often to move the refuse toward the end of the hopper opposite the location of the lift mechanism. Limiting the frequency of activation of the compactor greatly extends its useful life, thereby reducing the associated mechanical costs. Various attempts have been made to improve the ability of the lift mechanism to position the refuse cart as far back into the hopper as possible when inverted in the dump position. Examples of such attempts are disclosed in U.S. Pat. Nos. 4,365,922 and 4,422,814 to Borders, and U.S. Pat. No. 5,002,450 to Naab.
The problem with several of these approaches is that the lift mechanism sacrifices stability by overextending the lever arms past the longitudinal axis of the lift mechanism. As a result, the entire weight of the extended lever arm and the refuse cart is carried by one pivot point which greatly increases the wear associated with the lift mechanism.
Furthermore, several existing lift mechanisms are forced to choose between either a slender profile and a wide profile. Current technology is such that a slender profile lift mechanism sacrifices the ability to lift both residential and commercial refuse containers. Conversely, while wide profile lift mechanisms can handle both residential and commercial refuse containers, they sacrifice the ability to operate in confined areas. In addition, several of the existing lift mechanisms have a slender profile use a rotary actuator or similar mechanism to lift the refuse cart between the receiving and the dumping positions. The complexity of rotary actuators, the need to rotate the lift arms at least 180.degree. between the receiving and dumping position and the associated high costs of operation and maintenance makes such lift mechanisms less than ideal.
Moreover, various existing lift mechanism are either incapable of lifting the refuse cart a sufficient distance into the hopper of the refuse truck to minimize use of the compactor or they are forced to extend the lifting arms well beyond the midline of the lift mechanism. This in turn results in additional strain and wear on the device while making it unstable under load.